1. Field of the Invention
The present invention relates to an apparatus for measuring a thin film such as a resist thin film formed on a substrate such as a semiconductor wafer or a substrate for a flat panel display.
2. Description of the Background Art
Before a circuit pattern or the like is formed on a substrate in a step of manufacturing a substantially circular semiconductor wafer or a rectangular glass substrate, the substrate is coated with a photosensitive resist solution by the so-called spin coating. In this coating processing, the resist solution is discharged toward the substrate for forming a resist thin film on the surface of the substrate. In this method of forming the resist thin film by spin coating, part of the resist thin film is formed on an edge such as the upper surface, the side surface or the lower surface of an end of the substrate. When the part of the resist thin film formed on the edge of the substrate drops in a substrate processing apparatus during transportation or processing of the substrate, it follows that subsequent processing is badly influenced by particles or the like. In order to prevent this, edge cleaning processing (edge rinsing through an EBR (edge bead remover)) is generally performed for cleaning/removing the unnecessary part of the resist thin film formed on the edge of the substrate after the spin coating.
An apparatus executing the aforementioned edge cleaning processing on a substantially circular substrate such as a semiconductor wafer or a rectangular substrate is known as this type of apparatus.
When the resist solution is of a positive type, edge exposure may be employed as a method of removing the unnecessary part of the resist thin film formed on the edge of the substrate. In this edge exposure, the unnecessary part of the resist thin film formed on the edge of the substrate is exposed and thereafter removed by development processing.
In general, an operator visually inspects the state of removal of the unnecessary part of the resist thin film resulting from the aforementioned edge cleaning processing or edge exposure by microscopically observing the edge of the substrate thereby determining correctness thereof or the like.
In the aforementioned visual inspection by the operator, the results of inspection vary with the degree of experience or skillfulness of the operator, leading to a problem of incorrect inspection.